enh: enable message rating setting

backend/main.py

@@ -1973,6 +1973,7 @@ async def get_app_config():
             "enable_web_search": rag_app.state.config.ENABLE_RAG_WEB_SEARCH,
             "enable_image_generation": images_app.state.config.ENABLED,
             "enable_community_sharing": webui_app.state.config.ENABLE_COMMUNITY_SHARING,
+            "enable_message_rating": webui_app.state.config.ENABLE_MESSAGE_RATING,
             "enable_admin_export": ENABLE_ADMIN_EXPORT,
             "enable_admin_chat_access": ENABLE_ADMIN_CHAT_ACCESS,
         },